How will adding gypsum change the taste of my beer

Well, I've brewed my first two batches with very soft lake water from a deep cold clear Canadian Shield lake near my home.

Total hardness is only about 25ppm. Tap water the same (comes from the same lake before being treated). I've been told on here not to worry, that water that soft can brew beer just fine.

So I've taken that advice, and fermentation in both cases started within a day and has been vigorous. The first brew easily reached the final target of 1.008 to 1.010, and I've no doubt the nut brown will as well.

But at the LHBS yesterday to get a few more airlock valves and decided to pick up several ounces of gypsum.

If I add the gypsum, I'm very curious what changes I should expect from the flavor of my next beer, which is listed on deck below. It's using Nottingham yeast and Willamette hops. Thoughts?

You are adding Calcium, so it will give you a little saltiness if you add too much. If used properly, the additional hardness will enhance the hops.

http://www.howtobrew.com/section3/chapter15-4.html

Gypsum is Calcium sulfate, so you're not only adding calcium, but sulfate as well, which can enhance the hop profile.

Are you doing extract, partial mash or all grain? Gypsum is primarily used to lower pH of water AFTER it has been mashed with grain. Depending on your type of brew, you may end up with a "chalky" final product if you add too much.

my understanding is that harder water lends itself to a "crisper" perceived hop bitterness. I'm not sure how much difference you'll see in a cream ale, but there might be some. if you're up for an experiment, you can add the gypsum to half of the batch at bottling (dissolve a teaspoon in a little bit of boiling water and gently stir it into your bottling bucket after you've bottled about half the batch). you can then compare directly between bottles with and without gypsum to give you a feel for what it does.

we have fairly hard water here, but I still wind up adding gypsum to most of my beers. I've never done a direct comparison with/without it, maybe I'll have to split a batch some day and see.

So far, all three kits executed or planned are extract kits. The cream ale is the first kit using hops pellets. The first two it was hopped LME.

As for lowering the pH, I wasn't aware gypsum would do that. My pH is already between 6.5 and 7.

If your doing extract then the pH is not to worry about just yet. Gypsum use for an extract brewer will not be for pH but rather for the flavor and hop character which to me are kind of opinions of what you like. For a 5 gal batch at 1-2 tsp/ 4-8g of gypsum. See if you like it. It is my experience that within those limits you won't ruin any beer anyway so give it a shot.

I wouldn't be surprised if you get a better ferment and flocculation with more calcium in soft water, plus the hop crispness mentioned above from the sulphate. I think you would notice that more in an IPA or pale ale with more emphasis on hops.